This invention relates in general to electrical motors for submersible pumps, and in particular to a flexible bearing for maintaining the shaft of the rotor in alignment.
High volume wells, such as for oil or water production, often use a submersible pump. The pump is a centrifugal pump having a submersible motor that rotates a shaft to drive the pump. Often the motors have several hundred horsepower and are from six to sixty feet in length. Each motor has a stator secured within a tubular housing. A rotor secured to a shaft rotates within the stator.
Because of the long length, the rotor is made up of a number of sections. Each section comprises a large number of flat disks called laminations that are secured by copper rods. The sections are spaced-apart from each other, and a bearing is located between each section for maintaining the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation therewith, but are axially movable with respect to the shaft.
Each bearing assembly includes a sleeve keyed to the shaft for rotation therewith. A bearing member has a bore for rotatably receiving the sleeve. The bearing member has a periphery that frictionally engages the inner wall of the stator at operating temperatures to prevent the bearing member from rotating and to support the shaft in alignment.
As the motor heats up to operating temperatures, the bearing member will expand outwardly to frictionally engage the stator. The shaft will also grow longitudinally, causing the bearing member to move longitudinally with respect to the stator. The bearing member must be precisely dimensioned so that it does not engage the stator wall so tightly as to create excessive thrust loads on thrust washers located above and below the bearing member. For accurate dimensioning, the bearing is normally constructed of a metal with an outer wall ground to a 0.0005 inch tolerance. While satisfactory, this high tolerance makes the bearing member expensive. Also, should the bearing begin to spin with the shaft, its metal periphery may cause damage to the stator wall.